From 528bd6611776713fb8fc42c143e72480cd8b4f08 Mon Sep 17 00:00:00 2001
From: Andrew Cady <d@jerkface.net>
Date: Wed, 14 Aug 2024 16:31:49 -0400
Subject: implement pause/resume for input forwarding

---
 twopane.bash | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 73 insertions(+), 6 deletions(-)

diff --git a/twopane.bash b/twopane.bash
index d4d6459..0398ed7 100755
--- a/twopane.bash
+++ b/twopane.bash
@@ -174,7 +174,7 @@ background()
         connect stdin stdout
 }
 
-foreground()
+foreground_loop()
 {
         while true
         do
@@ -196,25 +196,92 @@ foreground()
         done
 }
 
-forward()
+forwarding()
 {
-        forward_input "$@"
+        [ "$FORWARD_PID" ] || return
+        FORWARD_JOBSPEC=$(jobs -sl | pid_to_jobspec "$FORWARD_PID")
+        [ "$FORWARD_JOBSPEC" ]
 }
 
-forward_input()
+forward()
 {
+        declare -g FORWARD_PID
         if ! check_top
         then
                 echo "$0: Warning: Nothing to forward.  Starting anew." >&2
                 background "$@"
+        elif forwarding
+        then
+                resume_forward
+                return
         fi
+
         focus top
-        socat FD:100,cfmakeraw!!STDOUT - <&$stdin |
-        tee >(output_filter | soft_cursor >&101) >&$stdout
+        old_stty=$(stty -g)
+        # Lowercase $stdin/$stdout are the SOCAT coprocess connected to
+        # the other pane's terminal.  Uppercase $STDIN/$STDOUT are the
+        # real stdin/stdout of this function, connected to the lower
+        # pane's terminal.  Socat here merges inputs from both sources.
+
+        # The input is put out raw back over the socket.  The input is
+        # copied to stdout after being filtered (to display control
+        # characters with carrot-encoding like '^[' etc).
+        exec {STDIN}<&0 {STDOUT}>&1 {STDERR}>&2
+        exec {TEE}> >(tee >(output_filter | soft_cursor >&$STDOUT) >&$stdout)
+        socat FD:$STDIN,cfmakeraw,opost=1,onlcr=1!!STDOUT - <&$stdin >&$TEE &
+        FORWARD_PID=$!
+        printf '%s\n' "#!/bin/bash" "kill $!" "screen -X focus bottom" > "$TWOPANE"/unforward
+        chmod +x "$TWOPANE"/unforward
+        fg
         stty "$old_stty"
         focus bottom
 }
 
+cfmakeraw()
+{
+        cmd=(stty -ignbrk -brkint -parmrk -istrip -inlcr -igncr -icrnl
+        -ixon -opost -echo -echonl -icanon -isig -iexten -parenb cs8)
+        "${cmd[@]}" "$@"
+}
+
+pid_to_jobspec()
+{
+        while read jspec pid status cmd
+        do
+                [ "$pid" = "$1" ] || continue
+                jspec=${jspec%]*}
+                jspec=%${jspec#[}
+                echo $jspec
+                return
+        done
+        false
+}
+
+resume_forward()
+{
+        old_stty=$(stty -g)
+        cfmakeraw opost onlcr
+        focus top
+        fg "$FORWARD_JOBSPEC"
+        stty "$old_stty"
+        focus bottom
+}
+
+foreground()
+{
+        if forwarding
+        then
+                resume_forward
+        else
+                foreground_loop "$@"
+        fi
+}
+
+twopane()
+{
+        start "$@"
+}
+
 quit()
 {
         screen -X quit
-- 
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